Sorry, I retract my comment above... it appears that the FDA says HIV can be transmitted through shared pumps, though there has been no recorded case so far. I'm still unsure how this is possible since it seems to contradict everything else we are told about how HIV can spread, but hey, if the FDA says it must be true!

However, hospital grade pumps are safe for sharing becuase they are a closed system whatever that means.

Knowing that HIV cannot live outside the human body for more than a minute or 2,
knowing that Hepatitis cannot live outside the human body for more than a few days
and chances of buying and using breast pumps in that short of a time is tiny, I think its being alarmist to suggest that purchasing of a used breastpump is a high risk activity.

We borrowed some and bought all we could second hand. If it was good enough for a friends baby, it was good enough for ours.

Breast pumps in hospitals are shared by all patients, breast shields there are getting sterilized after each use. Also milk bottles. What's different if you're buying them for home use? As said before, the pump doesn't get into contact with breast, all other parts can be sterilized or exchanged.

Same goes for potty or training toilet seat, they sure can be thoroughly cleaned! We are using a hand-me-down toilet seat at the grandparent's house.

Car seat I agree, you wouldn't know if it had been in an accident or been dropped, so might be unsafe.

Car seat I agree, you wouldn't know if it had been in an accident or been dropped, so might be unsafe.

Car seats (unlike cars) do not have internal hidden parts. If one has been in an accident it will be quite easy to see the damage associated with it.

As for getting dropped, that wont hurt it much. Think about:
a) airline baggage handlers and how your carseat gets shuffled along and dropped
b) delivery people who actually transported the car seat along. They regularly throw stuff around. Car seats are designed to widthstand such minor impacts.